What musical instrument did Leonardo da Vinci design with continuous bowing?

Leonardo da Vinci designed the viola organista, a keyboard instrument with continuous bowing.

The instrument combined a keyboard with a mechanism resembling the bowing action of string instruments. Pressing a key selected a string, while rotating wheels or a belt rubbed against the strings to produce sound. This allowed a player to control pitches from a keyboard while obtaining a sustained, bowed-string tone.

Leonardo drew several versions of the idea in his notebooks during the late fifteenth and early sixteenth centuries. No known original instrument built by Leonardo survives, and historians have debated details of how the mechanism was intended to operate. Modern makers have constructed working reconstructions based on his drawings.

The viola organista was not simply a mechanical viola or a conventional organ. It was an unusual hybrid joining keyboard control, string resonance, and continuous friction. Its name reflects the later description of the design rather than a standard instrument Leonardo himself is known to have publicly performed.